Magnetic memories, particularly magnetic random access memories (MRAMs), have drawn increasing interest due to their potential for high read/write speed, excellent endurance, non-volatility and low power consumption during operation. An MRAM can store information utilizing magnetic materials as an information recording medium. One type of MRAM is a spin transfer torque magnetic random access memory (STT-MRAM). STT-MRAM utilizes magnetic junctions written at least in part by a current driven through the magnetic junction. A spin polarized current driven through the magnetic junction exerts a spin torque on the magnetic moments in the magnetic junction. As a result, layer(s) having magnetic moments that are responsive to the spin torque may be switched to a desired state.
For example, a conventional magnetic tunneling junction (MTJ) may be used in a conventional STT-MRAM. The conventional MTJ uses seed layer(s), may include capping layers and may include an antiferromagnetic (AFM) layer to fix the magnetization of the reference layer. The conventional MTJ includes seed layer(s), a reference layer, a tunneling barrier layer, a free layer and a capping layer. A bottom contact below the MTJ and a top contact on the MTJ may be used to drive current through the MTJ in a current-perpendicular-to-plane (CPP) direction. The reference layer and the free layer are magnetic. The magnetization of the reference layer is fixed, or pinned, in a particular direction. The free layer has a changeable magnetization. The free layer and reference layer may be a single layer or include multiple layers.
To switch the magnetization of the free layer, a current is driven in the CPP direction. When a sufficient current is driven from the top contact to the bottom contact, the magnetization of the free layer may switch to be parallel to the magnetization of a bottom reference layer. When a sufficient current is driven from the bottom contact to the top contact, the magnetization of the free layer may switch to be antiparallel to that of the bottom reference layer. The differences in magnetic configurations correspond to different magnetoresistances and thus different logical states (e.g. a logical “0” and a logical “1”) of the conventional MTJ.
Because of their potential for use in a variety of applications, research in magnetic memories is ongoing. It is desirable to scale the magnetic junction to smaller areal dimensions (e.g. for increased memory density) without significantly degrading magnetic and electrical properties. For example, nonvolatile magnetic memories are desired to be scaled below forty nanometers. The operating temperatures for high operating temperature magnetic memory applications of magnetic memories are typically relatively high, for example, above one hundred degrees Celsius. The magnetic thermal stability factor, A, and thus the effective magnetic anisotropy constant, KUeff, are desired to remain high. Current magnetic junctions are unable to be scaled to such dimensions without adversely affecting one or more of the saturation magnetization, exchange stiffness, damping and/or effective magnetic anisotropy constant. Further, even at current dimensions, performance is desired to be improved.
Accordingly, what is needed is a method and system that may improve the performance and scalability of magnetic devices and the electronic devices in which such magnetic devices are used. The method and system described herein address such a need.